Apparatus for dispersing particulate materials

ABSTRACT

A method of, and apparatus for, dispersing particulate materials in fluids, particularly for dispersing materials e.g. polyacrylamide having particles which, if in contact on becoming wetted, agglomerate to form a non-dispersable mass. A vortex chamber is used to provide a hollow cylindrical rapidly flowing film of fluid onto the inner surface of which the material is introduced.

United States Patent Abbott June 12, 1973 APPARATUS FOR DISPERSING 2,843,293 7/1958 Burgoyne 222/129.4 PARTICULATE MATERIALS 3,133,675 5/1964 Broadhurst ZZZ/129.4 X 2,621,838 12/1952 Price ZZZ/129.4 Inventor: J Abbott, Burton-on-Trent, 2,843,293 7/1958 Burg0yne.... 222/129.4 England 3,446,399 5/1969 Ross et al. ZZZ/129.1 836,145 11/1906 Schutz 302/30 X [73] AS51211: Industry (Paems) Lmmed 2,513,382 7/1950 Tumbow et a1. 259/8 London, England 3,225,963 12/1965 Arpajian 222/334 x [22] Filed: Dec. 9, 1970 [21] Appl. No.: 96,507 Primary Examiner-Samue1 F. Coleman Att0rneyStevens, Davis, Miller & Mosher [30] Foreign Application Priority Data Dec. 23, 1969 Great Britain 62,655/69 ABSTRACT [52] U.S. Cl. 222/129, 259/8 A method of, and apparatus for dispersing particulate E 33 3255 5 materials in fluids, particularly for dispersing materials o e.g. polyacrylamide having particles which, if in con- 3O2/24 52; 259/4 tact on becoming wetted, agglomerate to form a non- 99 dispersable mass. A vortex chamber is used to provide a hollow cylindrical rapidly flowing film of fluid onto [56] References C'ted the inner surface of which the material is introduced.

UNITED STATES PATENTS 2,513,012 6/1950 Dugas 259/95 5 Claims, 3 Drawing Figures PAIENTEDJIINIZIW Y 3.738.534

SHEEI 2 I)? 2 FIG. 3.

APPARATUS FOR DISPERSING PARTICULATE MATERIALS This invention relates to methods of, and apparatus for, dispersing particulate materials in fluids.

In particular, although not exclusively, the invention relatesto methods of, and apparatus for, dispersing particulate materials having particles which, if in contact on becoming wetted, agglomerate to form a nondispersable mass.

One such particulate material is polyacrylamide which is used as a flocculating reagent in the treatment of coal.

A known method of dispersing polacrylamide in water requires slowly sprinkling the polyacrylamide by hand into a slow-moving current of water adjacent the vortex of a mixing tank. This method has the disadvantage of being time-consuming, especially as mixes must be made frequently. Hand-sprinkling frequently leads to the wastage of polyacrylamide because some of the particles become agglomerated and are then ineffective for flocculation purposes. Also, since it is difficult to estimate the amount of polyacrylamide wasted-due to agglomeration, the exact concentration of the mix is usually not known. The agglomerates may also lead to blockage of the feed pipes from the mixing or flocculation tanks.

In another known method of dispersing polyacrylamide in water, the material is periodically drawn through an orifice by a rapidly moving stream of water in contact with the orifice. Unfortunately, this method has the disadvantage that the particles adjacent to the orificebecome wetted and agglomerate while no water is flowing so that the orifice becomes wholly or partially blocked, which may prevent or hinder recommencement of material flow.

An object of the present invention is to provide an improved method of dispersing such particulate material in fluids which overcomes the above mentioned disadvantages.

Another object of the invention is to provide apparatus for carrying out the improved method of dispersing such particulate material in fluids. According to one aspect of the invention, in a method of dispersing particulate material in a fluid, a stream of relatively slow moving particles of the material is passed onto the inner surface of a hollow cylindrical film of the fluid which moves relatively rapidly both about the axis of, and from one end to the other of, the cylinder.

According to another aspect of the invention, apparatus for carrying out the above method of dispersing particular material in a fluid comprises a hollow vortex chamber having a tangential inlet for fluid at or adjacent one end of the chamber and adapted to cause the stream of fluid to form itself into a cylindrical film moving relatively rapidly bothabout the longitudinal axis of, and from the said one end towards the other end of the chamber, the film being confined by, and moving over,the inner cylindrical surface of the chamber, and means remote from the fluid which is arranged to release a stream of relatively slow moving particles of the material onto the inner surface of the film, the mixed fluid and material leaving the chamber at or adjacent the lower end thereof.

Advantageously, the longitudinal axis of the vortex chamber is inclined to the vertical plane, the said one end being uppermost. I

The means may comprise a vibrating chute having its discharge end positioned within the vortex chamber.

By way of example only, one embodiment of the invention will be described with reference to the accompanying drawings, in which:

FIG. 1 is a plan of a vortex chamber; and

FIG. 2 is a section along the line II of FIG. 1; and with reference to the accompanying drawing in which:

FIG. 3 is a diagrammatic sketch of automatically controlled equipment for mixing polyacrylamide with water.

In FIGS. 1 and 2 the vortex chamber 2 is shown to comprise a large diameter portion 4 having a tangentially-arranged water inlet pipe 6 and a small diameter portion 8 forming the outlet from the portion 4. An inner tube 10 extends from the wall of the portion 4 remote from the portion 8 to within the portion 8.

In operation of the vortex chamber 2, water is fed at relatively high pressure through the inlet pipe 6 from where it flows around the portion 4 moving inwards and increasing its speed until it reaches the diameter of the portion 8. The water then flows around the inner wall of the portion 8 in the form of a rapidly moving film covering all the surface of the wall. The film is held against the inner wall by strong centrifugal forces and is moved along the portion 8 as more water is fed into the chamber 2. Resulting from the large difference in the velocities of the fluid at the inner and outer surfaces of the film, large shear forces are created within the film. The portion 4 is of a sufficiently large diameter to ensure that turbulence due'to the inlet has decayed away by the time the water reaches the portion 8. The inner tube 10 forms only a guard to ensure that no water splashes towards the center of vortex chamber 2 and in alternative embodiments of the invention may be dispensed with.

In FIG. 3 the vortex chamber 2 is shown in an operational position constituting part of automatically controlled equipment for mixing polyacrylamide with water before it is fed to a stock tank (not shown) for a flocculant tank of a coal treatment plant.

The equipment comprises a mixing tank 12 having a central impeller 14 positioned below a distributing tube 16, and an outlet pipe 18 controlled by a valve 20. The tank 12 has a water inlet pipe 22 controlled by a valve 24 and fed from a constant head tank (not shown) and an inlet pipe 26 for the flocculating reagent. I

The inlet pipe 26 is connected to the portion 8 of the inclined vortex chamber 2 to which the water flow is controlled by a valve 28 in the inlet pipe 6.

Polyacrylamide is fed into the vortex chamber 2 from a vibrating chute 30, the material falls freely from the chute 30 which ensures that the particles are separated. Also the particles pass through atmospheric air which is sufficiently dry to prevent the particles of material becoming wetted and thus forming a non-dispersable mass on the chute 30. Hence blockage of the chute 30 is avoided.

As each particle of polyacrylamide falls onto the rapidly moving inner surface of the film of water, it is quickly moved by the fluid away from the point of contact before the following adjacent particle contacts the water. Thus the particles are prevented from becoming wetted while in contact with each other and agglomeration of the particles is avoided.

Immediately on contacting the water each particle is drawn into the water by the action of the inertia of the moving particle and by centrifugal force. The shear forces created within the film act on the particle tending to rotate it and ensuring that all the surface of the particle is wetted before the particle leaves the vortex chamber 2.

The chute 30 is fed from a small hopper 32. The amount of polyacrylamide in the hopper 32 is determined by a measuring pocket 34 having upper and lower gates 36, 38 respectively. Polyacrylamide is fed into the measuring pocket 34 from a large storage hopper 40.

The automatically controlled equipment operates in the following manner.

The stock tank is fitted with a liquid level sensing element which when the liquid falls to a predetermined level passes a signal to a timing control device 50 which is in electrical contact with all the operable parts of the apparatus by means (not shown) and which stops the impeller 14 and opens the valve to allow theflocculating reagent to drain from the mixing tank 12 into the stock tank. After a sufficient period of time has elapsed to ensure that the mixing tank 12 has emptied the control device shuts the valve 20 and opens valve'24, causing water to flow into the tank 12 until the impeller 14 is fully covered. The valve 24 is then closed by the control device and the valve 28 is opened causing water to flow into the vortex chamber 2 and out through the portion 8 and pipe 26 into the mixing tank 12. Next the control device starts the impeller 14 which causes the water to flow around the mixing tank 12 and which causes a current of air to be drawn down the center of the tank 12 and down the pipe 26. The air is then dispersed into the water in the tank 12. The current of air in the pipe 26 is such that when polyacrylamide is being fed into the vortex chamber 2 it carries relatively fine particles of polyacrylamide into the tank and prevents wastage. However, the relative large particles of polyacrylamide are substantially unaffected by the current of air and fall freely onto the film of fluid in the portion 8.

The control device then opens the lower gate 38 of the measuring pocket 34 allowing a predetermined amount of polyacrylamide to fall into the hopper 32. The vibrating chute 30 is then started so as to deliver the predetermined amount of polyacrylamide into the vortex chamber 2. The polyacrylamide is fed slowly along the chute 30 and allowed to fall freely on to the rapidly moving film of water flowing around and down the portion 8 of the vortex chamber 2. This freely falling, slow rate of feed ensures that the particles of polyacrylamide are separated from one another before they reach the rapidly moving film of water and become wetted. Thus the particles are dispersed in the water and agglomeration is prevented.

The mixture of water and the dispersed polyacrylamide particles is fed from the portion 8 through the pipe 26 directly into the impeller zone of the tank 12 wherethe mixture is further mixed by the action of the impeller 14 into the main volume of water in the tank 12.

When sufficient time has elapsed to ensure that the hopper 32 and the chute 30 are empty the control device stops the vibrating chute 30, closes the valve 28 and re-opens the valve 24 until the tank 12 is full.

The control device also closes the lower gate 38 of the measuring pocket 34 and opens the upper gate 36 allowing polyacrylamide to fall from the hopper 40 to till the measuring pocket 34. The upper gate 36 is then closed.

The impeller is then kept running for between 20 and 30 minutes before complete solution is achieved. After this time the reagent is ready for feeding to the stock tank when the level of liquid falls sufficiently to reinitiate the time sequence of the control device.

It can be seen from FIG. 3 that chute 30 is remote from any water flowing in the vortex chamber 2 so that it is impossible for the polacrylamide to become wet while on the chute 30. This ensures that no particles of polyacrylamide agglomerate together or stick on the chute 30. The inner tube 10 ensures that no water can splash towards the chute 30. In modifications of the equipment the inner tube 10 may be dispensed with.

In other embodiments of the invention the chute 30 is replaced by a screw feeder conveyor.

Alternatively any other suitable form of conveyor may be used.

In further alternative embodiments the particles of material may be projected into the vortex chamber from an air blowing device.

I claim:

1. Apparatus for dispersing particulate material in liquid comprising a hollow vortex chamber open at both its ends with an upstream portion of relatively large diameter and a downstream portion of relatively small diameter, the upstream portion having an upstream face and a downstream face which are transverse to the general direction of liquid flow, the said downstream face forming a step with the inner face of the downstream portion and the upstream face extending inwardly beyond the step, tangetially arranged inlet means for a liquid on the upstream portion of the chamber so that liquid substantially fills the upstream portion between the said upstream and downstream faces and overflows the said step to form a hollow film moving relatively rapidly around the general direction of liquid flow, the film being confined by, and moving over, the inner surface of the downstream portion of the chamber, particulate discharge means remote from the liquid to release a stream of relatively slow moving particles of the material onto the inner surface of the film, the mixed liquid and material leaving the downstream portion of the chamber at the end remote from the upstream portion.

2. Apparatus as claimed in claim 1, in which the longitudinal axis of the vortex chamber is inclined to the vertical plane, the upstream portion of the chamber being uppermost.

3. Apparatus as claimed in claim 2, in which the particulate discharge means comprises a vibrating chute having its discharge end positioned within the vortex chamber, the particulate material falling freely onto the film of liquid.

4. Apparatus for dispersing particulate material in a liquid, comprising a vortex chamber open at both ends with an upstream portion of relatively large diameter and a downstream portion of relatively small diameter, tangetially arranged inlet means of a liquid on the upstream portion of the chamber so that the stream of liquid forms itself into a hollow film moving relatively rapidly around the general direction of liquid flow, the film being confined by, and moving over, the inner surface of the downstream portion of the chamber, a vibrating chute for conveying particulate material, said chute having its discharge end positioned within the vortex chamber to release the material to fall freely at relatively slow speed onto the inner surface of the film, the mixed liquid and material leaving thedownstream portion of the chamber at the end remote from the upstream portion of the chamber, a stock tank arranged to receive the liquid and material leaving the chamber, outlet means from the tank for the mixed liquid and material, an impeller located within the tank and a pipe extending from the end of the downstream portion of the chamber remote from the upstream portion towards the impeller such that a current of air is drawn through the vortex chamber in the same general direction as the flow of liquid.

5. Apparatus for dispersing particulate material in a liquid comprising an inclined vortex chamber which is open at both its ends with an upper upstream portion having a relatively large diameter and a lower downstream portion having a relatively small diameter, the upstream portion having an upstream face and a downstream face which are transverse to the general direction of liquid flow, the said downstream portion and the upstream face extending inwardly beyond the step, tangentially arranged inlet means for a liquid provided on the upstream portion of the chamber so that liquid substantially fills the upstream portion between the said upstream and downstream faces and overflows the said step to form a hollow film moving relatively rapidly around the general direction of liquid flow, the film being confined by, and moving over, the inner surface of the said downstream portion of the chamber, means remote from the liquid to convey and release a stream of relatively slow moving particles of the material onto the inner surface of the film, the mixed liquid and material leaving the said downstream portion of the chamber at its lowermost end, a measuring pocket for determining the amount of particulate material fed onto the conveying means, a stock tank arranged to receive the mixed liquid and material leaving the downstream portion of the chamber, outlet means from the tank for the mixed liquid and material, an impeller located within the tank, and a timing control device which automatically controls the operation of the apparatus. 

2. Apparatus as claimed in claim 1, in which the longitudinal axis of the vortex chamber is inclined to the vertical plane, the upstream portion of the chamber being uppermost.
 3. Apparatus as claimed in claim 2, in which the particulate discharge means comprises a vibrating chute having its discharge end positioned within the vortex chamber, the particulate material falling freely onto the film of liquid.
 4. Apparatus for dispersing particulate material in a liquid, comprising a vortex chamber open at both ends with an upstream portion of relatively large diameter and a downstream portion of relatively small diameter, tangetially arranged inlet means of a liquid on the upstream portion of the chamber so that the stream of liquid forms itself into a hollow film moving relatively rapidly around the general direction of liquid flow, the film being confined by, and moving over, the inner surface of the downstream portion of the chamber, a vibrating chute for conveying particulate material, said chute having its discharge end positioned within the vortex chamber to release the material to fall freely at relatively slow speed onto the inner surface of the film, the mixed liquid and material leaving the downstream portion of the chamber at the end remote from the upstream portion of the chamber, a stock tank arranged to receive the liquid and material leaving the chamber, outlet means from the tank for the mixed liquid and material, an impeller located within the tank and a pipe extending from the end of the downstream portion of the chamber remote from the upstream portion towards the impeller such that a current of air is drawn through the vortex chamber in the same general direction as the flow of liquid.
 5. Apparatus for dispersing particulate material in a liquid comprising an inclined vortex chamber which is open at both its ends with an upper upstream portion having a relatively large diameter and a lower downstream portion having a relatively small diameter, the upstream portion having an upstream face and a downstream face which are transverse to the general direction of liquid flow, the said downstream portion and the upstream face extending inwardly beyond the step, tangentially arranged inlet means for a liquid provided on the upstream portion of the chamber so that liquid substantially fills the upstream portion between the said upstream and downstream faces and overflows the said step to form a hollow film moving relatively rapiDly around the general direction of liquid flow, the film being confined by, and moving over, the inner surface of the said downstream portion of the chamber, means remote from the liquid to convey and release a stream of relatively slow moving particles of the material onto the inner surface of the film, the mixed liquid and material leaving the said downstream portion of the chamber at its lowermost end, a measuring pocket for determining the amount of particulate material fed onto the conveying means, a stock tank arranged to receive the mixed liquid and material leaving the downstream portion of the chamber, outlet means from the tank for the mixed liquid and material, an impeller located within the tank, and a timing control device which automatically controls the operation of the apparatus. 